The most common light source for atomic absorption spectroscopy is a hollow cathode lamp (HCL). In the past, several intensive efforts were attempted to construct alternate light sources, mainly electrodeless discharge lamps (EDL). However, in spite of the extreme high intensity and the concentration of the high intensity on resonance lines, these lamps are not always used in atomic absorption spectroscopy. The main reasons these lamps are not always used are: (1) lack of intensity stability, and (2) a very short life.
Discharge lamps utilized in spectroscopy are illustrated, for example, in German Patentschrift DE 3005 638 and U.S. Pat. No. 3,686,529 incorporated herein by reference. DE 3005 638 discloses a lamp design with internal heating of the discharge path T1 and the reserve section T2, with the temperature of the discharge path T1 being higher than that of the reserve section T2. U.S. Pat. No. 3,686,529 shows a glow discharge lamp with separate power supplies for the lamp current and heater to provide an operating temperature independent of operating current.